1. Field of the Invention
The present invention relates to an ink jet recording method, a recording unit, an ink jet recording apparatus and the like.
2. Related Background Art
Conventionally, ink for writing implements (fountain pens, nylon-tip pens, water ball-point pens, etc.) and ink for ink jet, which use carbon black high in print density and excellent in solidness or the like as a black coloring agent for printing ink, have been reported in various compositions. Among them, in recent years, detailed research and development have been carried out on compositions and physical properties of carbon blacks themselves, compositions and physical properties of ink containing the carbon black, and the like such that recording can be made satisfactorily on plain paper such as copy paper, reporting paper, notebook paper, writing paper, bond paper and continuous slip paper that are generally used in offices.
For example, ink that uses acid carbon black and alkaline soluble polymer is described in Japanese Patent Application Laid-open No. 3-210373. In addition, ink for ink jet with which dispersion excellent in preservation stability and dischargeability in a bubble jet recording apparatus tends to be realized is described in Japanese Patent Application Laid-open No. 3-134073.
In addition, Japanese Patent Application Laid-open No. 8-3498 presents technical problems such that ink containing a dispersing agent together with carbon black is unstable in discharge as ink for ink jet and cannot realize a sufficient print density, and discloses ink using self-dispersing carbon blacks that can disperse in a solvent without using a dispersing agent as ink capable of solving the problems. International Patent Publication No. 96/18695 (Japanese Patent Application Laid-open No. 10-510862) and U.S. Pat. No. 5,746,818 (Japanese Patent Application Laid-open No. 10-95941) also disclose ink for ink jet containing self-dispersing carbon blacks and describe that high quality images can be obtained using the ink.
Moreover, in European Patent Publication No. EP943666, inventors of the present invention disclose technical means for adding salt to ink in addition to the above-mentioned self-dispersing carbon blacks for the purposes of improving paper type dependency of an image density, reducing bleeding in a boundary between black and color, and the like in using the above-mentioned self-dispersing carbon black as ink for ink jet.
Incidentally, concerning conventional pigment ink, it is known that discharge stability may be lost. More specifically, for example, when ink is discharged from a predetermined nozzle of an ink jet recording head and then the ink is discharged again from the nozzle after the discharge of the ink from the nozzle is stopped for a certain length of time (e.g., 12 hours), the re-discharge of the ink may not be stable, whereby printing is collapsed (operations for discharging ink from a predetermined nozzle and discharging the ink again from the nozzle after stopping the discharge of the ink from the nozzle for a predetermined length of time is hereinafter referred to as xe2x80x9cintermittent discharge of inkxe2x80x9d and a state in which re-discharge of ink is unstable is hereinafter referred to as xe2x80x9cpoor in intermittent dischargeabilityxe2x80x9d).
In addition, when ink is discharged again from a nozzle after discharge of the ink from the nozzle is stopped for a long time of period (e.g., a few days or more), a recovery operation for removing ink having increased viscosity or solidified in the nozzle may be required (a state in which re-discharge of ink is unstable due to increase in viscosity or solidification of ink in a nozzle is hereinafter referred to as xe2x80x9clocking of inkxe2x80x9d and a state in which a recovery operation is required many times for realizing stable re-discharge is hereinafter referred to as xe2x80x9cpoor in retentivityxe2x80x9d).
As described above, properties required of black ink for ink jet need to be extremely sophisticated in accordance with the need for images recorded by ink jet to be very high in quality in recent years. However, concerning pigment ink containing the above-mentioned self-dispersing carbon black as a coloring material, it cannot be said that technical knowledge for giving a high OD and a sharp edge and attaining excellent ink jet discharge properties such as intermittent dischargeability and retentivity is sufficiently attained. Thus, some of the characteristics of such pigment ink as ink for ink jet recording are unclear.
On the other hand, various improvements have been made on a configuration of an ink jet recording head. A configuration in which a movable member for regulating a flow of liquid (ink) and a growing direction of a bubble is provided in a bubble generation area in a liquid flow path is disclosed, for example, in Japanese Patent Application Laid-open Nos. 2000-62180, 2000-62181 and 2000-62182.
For example, the above-mentioned ink containing self-dispersing carbon blacks and salt disclosed by the inventors of the present invention is extremely effective for reducing paper type dependency of an image density and reducing bleeding in a boundary area between black and color in an image, which is an initial object. However, as a result of further study aiming at establishing a more excellent ink jet recording technology by the inventors of the present invention, large fluctuations are sometimes found in the intermittent dischargeability and the retentivity of the ink depending on a structure of a recording head used.
On the other hand, in an ink jet recording head having the configuration in which a movable member is provided in a liquid flow path, a changing rate of a changing point from growth to contraction of a bubble in the liquid flow path is stabilized and quick separation of liquid being ejected is satisfactory and stabilized, whereby the printing grade can be improved. However, with ink using self-dispersing pigment, the pigment is deposited on such a movable member due to agitation or the like of liquid by the movement of the movable member, and the initial stability in the movement of the movable member cannot be secured as the amount of deposition increases, whereby dischargeability may be changed.
Now that a structure of a recording head is expected to be diversified in accordance with wide product development of ink jet printers and expansion of areas in which ink jet recording technology is to be applied in the future, it has been recognized that development is required for ink showing a satisfactory and stable ink jet property with respect to the diversification of recording heads while making use of excellent properties of ink containing self-dispersing carbon blacks.
The present invention has been devised in view of the above-mentioned drawbacks, and it is an object of the present invention to provide an ink jet recording method, a recording unit and an ink jet recording apparatus that have excellent properties as regards the intermittent dischargeability and the retentivity of ink.
In addition, it is another object of the present invention to provide an ink jet recording method, a recording unit, an ink jet recording apparatus and the like that can steadily obtain high quality prints.
An ink jet recording method in accordance with the present invention is an ink jet recording method having steps of giving energy to ink, discharging the ink from a recording head and depositing the ink on a recording medium, which is characterized in that;
the ink is ink containing a coloring material including at least self-dispersing carbon blacks, which are formed of at least one hydrophilic group bonded to a surface of a carbon black directly or via another atom group, and an aqueous medium and further having potassium ions of 0.6% or more in a mass ratio with respect to the carbon blacks; and
the recording head includes a structural unit for discharging liquid droplets having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble, and the ink is supplied to the liquid flow path and discharged from the discharge port by thermal energy from the heating element.
In addition, an aspect of a recording unit in accordance with the present invention is a recording unit provided with an ink containing portion in which ink is contained and a recording head portion for discharging the ink as ink droplets, which is characterized in that;
the ink is ink containing a coloring material including at least self-dispersing carbon blacks, which are formed of at least one hydrophilic group bonded to a surface of a carbon black directly or via another is atom group, and an aqueous medium and further having potassium ions of 0.6% or more in a mass ratio with respect to the carbon black; and
the recording head includes a structural unit for discharging liquid droplets having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble.
An aspect of an ink jet recording apparatus in accordance with the present invention is an ink jet recording apparatus provided with a recording unit having an ink containing portion in which ink is contained and a recording head portion for discharging the ink as ink droplets by an action of energy, which is characterized in that,
the ink is ink containing a coloring material including at least self-dispersing carbon blacks, which are formed of at least one hydrophilic group bonded to a surface of a carbon black directly or via another atom group, and an aqueous medium and further having potassium ions of 0.6% or more in a mass ratio with respect to the carbon black, and
the recording head includes a structural unit for discharging liquid droplets having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble, and the ink is supplied to the liquid flow path and discharged from the discharge port by thermal energy from the heating element.
Another aspect of the ink jet recording apparatus in accordance with the present invention is an ink jet recording apparatus provided with an ink cartridge including an ink containing portion in which ink is contained and a recording head for discharging the ink as ink droplets by an action of energy, which is characterized in that;
the ink is ink containing a coloring material including at least self-dispersing carbon blacks, which are formed of at least one hydrophilic group bonded to a surface of a carbon black directly or via another atom group, and an aqueous medium and further having potassium ions of 0.6% or more in a mass ratio with respect to the carbon black, and
the recording head includes a structural unit for discharging liquid droplets having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble, and the ink is supplied to the liquid flow path and discharged from the discharge port by thermal energy from the heating element.
Another aspect of the ink jet recording method in accordance with the present invention is an ink jet recording method having steps of giving energy to ink, discharging the ink from a recording head and depositing the ink on a recording medium, which is characterized in that;
the ink is ink containing self-dispersing pigment having a hydrophilic group as a coloring material and also containing counter ions with respect to the hydrophilic group and ions with hydration force lower than that of the hydrophilic group while having a polarity opposite that of the hydrophilic group in addition to the counter ions; and
the recording head consists of a configuration having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble, and the ink is supplied to the liquid flow path and discharged from the discharge port by thermal energy from the heating element.
Another aspect of the recording unit in accordance with the present invention is a recording unit provided with an ink containing portion in which ink is contained and a recording head portion for discharging the ink as ink droplets, which is characterized in that;
the ink is ink containing self-dispersing pigment having a hydrophilic group as a coloring material and containing counter ions with respect to the hydrophilic group and also ions with hydration force lower than that of the hydrophilic group while having a polarity opposite that of the hydrophilic group in addition to the counter ions; and
the recording head consists of an ink jet head having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble.
Another aspect of the ink jet recording apparatus in accordance with the present invention is an ink jet recording apparatus provided with a recording unit having an ink containing portion in which ink is contained and a recording head portion for discharging the ink as ink droplets by an action of energy, which is characterized in that,
the ink is ink containing self-dispersing pigment having a hydrophilic group as a coloring material and containing counter ions with respect to the hydrophilic group and ions with hydration force lower than that of the hydrophilic group while being in a polarity opposite that of the hydrophilic group in addition to the counter ions, and
the recording head consists of an ink jet head having a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble.
Another aspect of the ink jet recording apparatus in accordance with the present invention is an ink jet recording apparatus provided with an ink cartridge including an ink containing portion in which ink is contained and a recording head for discharging the ink as ink droplets by an action of energy, which is characterized in that;
the ink is ink containing self-dispersing pigment having a hydrophilic group as a coloring material and containing counter ions with respect to the hydrophilic group and also ions with hydration force lower than that of the hydrophilic group while having a polarity opposite that of the hydrophilic group in addition to the counter ion; and
the recording head has a heating element for generating thermal energy for generating a bubble in liquid; a discharge port that is a portion for discharging the liquid; a liquid flow path communicating to the discharge port and having a bubble generation area for generating a bubble in liquid; and a movable member that is provided facing the bubble generation area and is displaced following growth of the bubble.
According to the present invention, a flow area in which a cross section of a liquid flow path of a recording head is sharply narrowed is formed by a configuration having a movable member and a regulating portion provided in the liquid flow path, where by locking of solids due to evaporation of a solvent component of ink or the like and deterioration of discharge performance are stemmed, and thus stability of discharge and discharging power can be maintained even if recording is resumed after leaving the recording head unused. In addition, concentration of carbon black is prevented by existence of potassium ions contained in the ink and a more superior locking prevention effect is realized. Therefore, an excellent property can be obtained with respect to the intermittent dischargeability (ejection stability in intermittent ejection) and the retentivity by a combination of ink with a specific composition and a recording head having independent actions in the upstream side and the downstream side divided by a heating element in the middle.
On the other hand, if the movable member is provided facing the heating element in the recording head used in the present invention, components of ink on the heating element, in particular the amount of moisture, are retained at a relatively high ratio even if a solvent component or the like of the ink evaporates from the discharge port. Thus, since stability of bubbling is maintained in this area, decrease of the discharging power can be prevented. Since concentration of carbon blacks is avoided by potassium ions also in an area from the discharge port to the movable member and the regulating portion, the degree of locking of solids can be effectively suppressed to an extremely low level. Therefore, excellent properties can be obtained with respect to the intermittent dischargeability (ejection stability in intermittent ejection) and the retentivity by a combination of ink with a specific composition and a recording head having independent actions in the upstream side and the downstream side divided by a heating element in the middle.
Moreover, if solvent or the like of ink evaporates from the discharge port of the recording head, a flow path resistance that is different between the upstream side and the downstream side of the heating element in the middle becomes overwhelmingly large on the discharge port side. However, in the present invention, since the space between the movable member and the regulating portion is substantially closed at the time of bubbling by actions of these portions, the flow path resistance becomes extremely large on the upstream side despite the evaporation, whereby there is no loss of power on the discharge port side. In particular, since concentration of carbon blacks is avoided by potassium ions in the area from the discharge port to the movable member and the regulating portion as well, a degree of locking of solids can be effectively suppressed to an extremely low level. Therefore, excellent properties can be obtained with respect to the intermittent dischargeability (ejection stability in intermittent ejection) and the retentivity by a combination of ink with a specific composition and a recording head having independent actions in the upstream side and the downstream side divided by a heating element in the middle.